Counterbalance springs for double-hung window sash have been stretched between an anchorage at the top of a jamb liner and a platform engaging a lower corner of the sash, and a cover attached to the jamb liner has concealed the spring in the upper half of the sash run. Especially for jamb liners and spring covers formed of extruded resin material, a desirable way of attaching the spring cover to the jamb liner has been by interlocking opposite back edges of the spring cover with a pair of guide rails extending along the sash run of the lamb liner. Such spring systems have been assembled with jamb liners for shipment to window manufacturers who install the jamb liners and spring system within a window frame containing double-hung window sash.
The covers of such window balance spring systems sometimes come loose from the guide rails in the jamb liners and require laborious reattachment. This can sometimes happen even after the complete window assembly is installed in a building.
I have devised a simple, low cost, and effective way of preventing the spring cover from coming loose from the jamb liner, and my solution for this problem has led to unexpected additional advantages. For example, window counterbalance spring systems can be subassembled into my improved spring cover, which reliably holds all the components together and participates in the secure attachment of all the components to a jamb liner. My invention thus saves labor costs, makes manufacturing assembly more efficient, and eliminates losses from spring covers working loose from jamb liners.